Increase In West Nile Caused By Weather

September 10, 2012

ITHACA - An expert on mosquito-borne diseases says early season heat has contributed to an increase in West Nile Virus infections in New York state.

"We are concerned that hotter than normal temperatures this summer may be responsible for accelerating viral replication in mosquitoes capable of transmitting the virus leading to an earlier and greater number of human cases and virus-positive mosquitoes," said Laura C. Harrington, associate professor of entomology at Cornell University and mosquito-borne disease expert. "With no vaccine and no specific treatment for West Nile virus, the best prevention is to minimize exposure to mosquito bites through use of repellents, limit outdoor activity and eliminate mosquito breeding sites."

Harrington said, through Aug. 23, a total of 11 confirmed human cases of West Nile Virus have been reported in New York state, including one death in Onondaga County. To date, 714 mosquito pools have tested positive for the virus across the state.

"Late August is typically a time when the number of human cases starts to escalate quickly," said Harrington. "This annual trend is most likely due to gradual amplification of the virus over the course of the summer in bird populations, leading to increases in the number of infectious mosquitoes."

As a consequence, we are likely only at the beginning of a significant upward trajectory in human cases."

While Harrington's statement is particularly unnerving, Mark Stow, Chautauqua County director of environmental health, has provided some insight into the nature of the virus and the mosquitoes which carry it.

"While I would like to say that I'm not aware of any confirmed human cases of West Nile Virus in (Chautauqua County) ever, there are still steps which can and should be taken to contribute to the decline of the mosquito population," said Stow. "If we're going to emphasize anything here, it's that these are not your typical flood plane mosquitoes where the water rises and the mosquitoes breed in pools. These mosquitoes breed in discarded tires and other man-made garbage which (is left out to rot)."

County residents who have not been vigilant to prevent the West Nile in the past few years are being asked to make sure pools of standing water, where mosquitos breed, is eliminated. Stow said tires that have been left outdoors for a few years can have organic matter build up inside that makes them attractive to mosquitos.

"Predominantly, mosquitoes breed in these tires in great number and then would come in contact with the virus through usually a bird host, where they then become a threat to pass the virus onto humans," Stow said. "The key is eliminating standing water around the house. Get rid of these tires, make sure that the water is drained out of them. Drill holes in them, put them in the garage or take them to the landfill, but do not allow them to just sit out. I think we're our own worst enemy when it comes to this disease, because even an (aluminum can) that is allowed to sit out and accumulate grass or leaves could serve as a breeding ground for these mosquitoes."

Stow said that while the weak winter helped contribute to the rampant nature of the disease and that a "normal winter" this year could help to curb West Nile cases, he said the disease is here to stay. Much like sunscreen on a hot day, bug repellent should be applied whenever potential contact with mosquitoes could occur.